Centering apparatus for well bore conduits



United States ...Patent 0 if@ CN'IERING APPARATUS FOR WELL BORE CONDUITS The present invention relatesto apparatus for centering strings of well casing, and similarconduit strings, in well bores.

`It is desirable to secure the substantial central disposition of a string of well casing in a well bore to insure the obtaining of a good cement job, through the proper placing of cement `completely around the wellv casing. Some centering devices-employ outwardly bowed springs mounted on the casing, that engage the wall of the well bore and tend to hold the casing string approximately in a central position therein. To be elective, the bowed height of each spring yshould besuch that the spring bears upon the wall of the well bore and exerts sucient centering force on the well casing to shift it toward a centered position.

When springs of suicient bowed height are used, they are sometimes diiiicult to start in the surface casing at the top of the hole, especially when there is comparatively small clearance between the surface casing and the casing on which the centering springs are mounted.

This is due to the force required to collapse the springs inwardly toward the casing on which they are mounted. In addition, a large extent of inward deflection or collapse of the springs causes the outward force exerted by them against the surface casing to be high, resulting in high sliding friction between the surface casing and springs that might cause excessive wear on the springs and their possible breaking. Moreover, the large inward deection of the springs might result in their permanent inward `flattening or deformation, rendering them incapable of centering the well casing when loweredinto open hole below the surface casing. t

Accordingly, it is an object of the present invention to provide a casing centering device embodying outwardly bowed springs, which can be started easily in, and moved easily through, surface casing, and in which the springs still have the desired outwardly bowed height and capability 'of exerting suiilcient centeringforcewhen disposed in an open hole. t

Another object of the invention is Vto provide a casing centering device embodying outwardly bowed -springs that are normally disposed in a relative inward position, and in which the bowed height and centering `force of the springs can be increased whenever desired. In'this manner, the springs can be retained initially ina relatively retracted position, with a comparatively small or zero bowed height, during the complete lowering of the casing string in the well bore, after `which the springs are expandible outwardly against the wall of the well bore to secure shifting of the casing string `toward a centered position.

t A further object of the invention is to provide a` casing centering device embodying outwardly bowed springs that can be expanded outwardly, when desired, against the wall of a well bore to exert a predetermined centering force on the well casing, such force-being prevented from exceeding av particular maximum value, to insure against overstressing of the springs. l

a 2,832,421 Patented Apr. 29, 1958 Yet another object of the invention is to provide a casing centering device embodying outwardly bowed springs, or the like, which are expandible outwardly in response to hydraulic pressure within the casing string.

This invention .possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, sincethe scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section through an apparatus embodying the invention attached to a string of well casing, the parts being disclosed in an initial retracted position;

Fig. 2 is a view similar to Fig. l, disclosing the spring portions of the centering device in their expanded position;

Fig. 3 is an enlarged fragmentary longitudinal section through a portion of the device shown in Figs. 1 and 2.

The apparatus disclosed in the drawings: is intended to hold a string of well casing in a substantially centered position within a well bore. In accomplishing this purpose, a plurality of circumferentially spaced outwardly bowed leaf springs are caused to bear against the wall of the well bore, the springs urging the` casing string toward a centered position in the well bore.

Initially, the springs occupy a substantially inward or retracted position, so as to be movable very easily through surface casing and, for that matter, through the well bore itself. However, whenever it is desired to expand the springs against the wall of the well bore, they are shiftable outwardly to exert a substantial centering force, which preferably does not exceed a predetermined maximum value.

In the specific form disclosed in the drawings, a tubular body 10, which may actually constitute a casing section or nipple, has an upper threaded box 11 threadedly secured to the lower pin end 12 of an upper casing section 13 forming part of the casing string to be lowered in the well bore. The lower end of the tubular body has a threaded pin 14 formed thereon threadedly received within a coupling or collar 15, the ylower end of this co1- lar being threaded onto the `upper pin end 16 of a lower` casing section 1'7.

A plurality of circumferentially spaced outwardly bowed springs 18 is disposed around the tubular casing body. The'lower ends 19 of the springs may be secured to a lower collar 20 through the use of welding material 21,` the lower collar itself being suitably secured to the body, as by use of -welding material 22. The upper ends 23 of the springs are received Within an upper collar or hydraulic -cylinder 24 that is slidable along the periphery of the tubular body 10. The upper ends 23 of the springs 18 extend within a skirt 25 depending from the cylinder, engaging a cylinder head or shoulder 26 which is slidable `along the exterior of the body 1t). The cylinder above the head 26 is constituted by a skirt 27 having a larger internal diameter than the head, for the purpose' of sliding along an enlarged head portion 23 of the body `Initially, the cylinder 24 occupies an yupper position on `the body 10, the cylinder head 26 being disposed adjacent the lower 'end 29 of the enlarged body head 28. One or more side ports 30 -extend through the body immediately'below the vbody head 28 for the purpose-of feeding fluid under pressure from the interior of the casing string and the body 10 into the cylinder space 31` assai-a1 formed between the body 10 and the cylinder 24. Leakage of fluid in a downward direction out of the cylinder space 31 is prevented by providing a suitable side seal 32, such as a rubber or rubber-like O ring, in a circumferential groove 33 in the head 26 which slidably engages the periphery of the body 10. Leakage of iluid in an upward direction out of the cylinder space 31 is prevented by providing a suitable side seal 34, such as a rubber or rubber-like ring, in a circumferential groove 35 in the skirt 27 which 'slidably engages the periphery of the body head 2B.

When unrestrained, the springs 18 occupy a position that is comparatively retracted, with the mid-portions 36 of the springs having only a relatively small bowed height 37 with respect to the exterior ofthe body 10. When in this position, the upper ends 23 of the springs engage the cylinder head 26 to hold the cylinder 24 in its initial upward position. Of course, if desired, the initial shape of the springs 18 may be comparatively flat, there being substantially no outwardly bowed height to the midportions E36 of the springs. However, it is desired to have a slight bowed height, inasmuch as the outward expansion of the springs is facilitated, as explained hereinbelow.

When the apparatus is run in the well bore, there is no fluid under pressure within the casing string, the cylinder 24 remaining in its upper position on the body lil, and the springs 1d retaining their comparatively lattened position, such as shown in Fig. 1. When the casing string has been lowered in the well bore A to the desired depth, centering of the casing in the well bore is accomplished by causing the springs 1li to expand outwardly against the Wall of the Well bore. The uid in the Well casing 13, is subjected to pressure, this fluid under pressure passing outwardly through the ports 3l) and into the cylinder space 31, urging the cylinder 24 downwardly along the body lll, the cylinder head 26 engaging the upper ends 23 of the springs 18 and forcing such upper ends of the springs downwardly toward the lower ends 19 of the springs. As a result of such shortening in the overall length of the springs, the midportions 36 of the springs are caused to bow outwardly into engagement with the wall of the well bore A. The force exerted by the bowed springs against the wall of the well bore depends upon theextend of movement of the upper cylinder or collar 24 toward the lower collar 20. As the spring force is increased, it acts reactively on the casing, tending to center it in the well bore.

Following bleeding oil or relieving of the pressure within the casing string, the outwardly bowed springs 18 would tend to retract, shifting the upper collar or cylinder 24 back to its initial position. Such return shifting is precluded through the provision of a one-way lock device between the upper collar 24.- and the body 1t? of the tool. As disclosed, the cylinder sleeve 27 above the side seal groove 35 is provided with an internal groove 40, the base 4l of which tapers in an upward and outward direction, ending in a shoulder 42 which constitutes the upper end of the groove. Disposed within the groove 40 is a split ring d3 that tends inherently to contract into engagement with the head 28 of the body lt). The inner surface of this split ring may have wiclters or teeth 44 formed therein facing in an upward direction and tending to grip the periphery of the body head. The outer surface 45 of the ring is tapered in an upward and outward direction, conforming to the taper 41 of the bottom of the groove 40.

When the cylinder 24 is moved downward by hydraulic pressure, for the purpose of expanding the springs 18 outwardly into engagement with the wall of the well bore A, to bear thereagainst with substantial spring force, the upper tlange or shoulder 42 of the sleeve 27 carries the split ring 43 downward with it, the split ring tending to be disposed in the comparatively wide portion of the groove 40, in which position it cannot prevent the downward movement of the cylinder 24 along the body 10 of the tool. However, after the cylinder' 24 has moved downward of the body 10 to expand the springs 18, the latter are tending to reshift the cylinder in an upward direction. Such action, however, causes the tapered surface 41 of the sleeve 27 to engage the companion surface 45 of the split ring 43, urging the latter inwardly into iirm gripping engagement with the body of the tool, the ring 43 thus preventing upward movement of the cylinder 24, and, in fact, effecting a locking of the cylinder 24 to the body 10.

During lowering of the casing string in the well bore, and prior to the imposition of uid pressure on the cylinder head 26, upward movement of the cylinder 24 on the body 10 is limited by engagement of the cylinder flange 42 with a companion shoulder 28a on the body head 2S.

It is, therefore, apparent that the casing string can be run in the well bore A, with the springs 13 in their initial retracted position, and that the springs 18 can be shifted positively in an outward direction by the force of the fluid under pressure within the casing string whenever desired, the springs remaining in their outward position in view of the action of the lock ring 43 in preventing yreturn upward movement of the cylinder 24 along the body 10. The fluid under pressure can be provided in any manner. For example, if the casing below the ports 30 is closed, the pressure of the fluid can be built up. However, it is desired that the pressure of the fluid imposed upon the cylinder head 26 be limited in degree, to prevent the imposition of too great a force on the springs 18 tending to expand them outwardly, which might, if excessive, cause the springs to break.

In the present instance, a limitation is placed on the pressure that can be imposed upon the cylinder 24. Thus, a plug 59 is disposed in the casing to restrict the downward passage of fluid therethrough at some convenient point below the ports 30. This plug may include a plug body 51 having an outwardly directed ange 52 adapted to be received within the coupling space 53 between the body 10 of the tool and the lower casing section 17. A suitable side seal 54 may be provided in the body 51 of the plug for sealing engagement with the inner wall 55 of the body 10. The body of the plug is provided with a comparatively large central passage or opening 56, which is normally closed by a shearable or rupturable disc 57 extending completely across the passage, its outer portion being received within a circumferential groove 58 encompassing the plug passage 56. This disc may be made of any suitable material which will rupture or shear out under a predetermined pressure. For example, it may be made of lead. It is preferred that an orice S9 be provided through the disc 5'7, which will allow tluid to enter the string kof casing as it is being lowered in the well bore A.

When-the location in the well bore is reached at which it is desired to expand the springs 18 outwardly, tluid is pumped down through the casing string. In View of the throttling action of the orifice 59 through the disc 57, aback pressure is built up in the casing string above the plug 50, this tluid under pressure passing outwardly through the-body ports 30 and into the cylinder space 31, acting in a downward direction on the cylinder 24 and urging it toward the lower collar 20, to foreshorten the over-all length of the springs 18 and bow them outwardly against the wall of the well bore A. The pressure of the lluid in the casing string is increased until it reaches a predetermined value at which it will burst or shear the lead disc 57 completely from the passage 56 (Fig. 2). Such action will occur at a predetermined pressure, depending upon the dimensions of the disc 57 and the size of the orice 59. But when it does occur, it will relieve the tluid in'the well casing of pressure and consequently preclude any further application of expanding force to the cylinder 24v and the outwardly bowed vsprings 18. Thus, the springs 18 cannot be expanded outwardly with ahydraulic forcethat exceeds a predetermined maximumvalue, thereby preventing the imposition of inordinately high expanding forces von the springs that might result in their destruction. Once the springs are expanded outwardly, the lock arrangement 40-45 will hold them in such outwardly expanded position.

When the shearable or rupturable disc 57 is removed from the passage, uid canbe pumped down through the casing string for discharge at a lower point therefrom, and for subsequent upward passage through the annulus between the casing string and the wall of the well bore. Such fluid may be cement slurry, which will be deposited uniformly around the centered casing string.

If desired, a plurality of the casing centering devices may be provided along the length of the casing string at predetermined intervals. Only a single shearable disc 57 and plug 50 is necessary, being disposed below the ports 30 of the lowermost casing centering device. After the casing string `has been lowered to the desired point in the well casing, the application of pressure to the lluid in the Well casing will effect a simultaneous expansion of the springs 18 of the several centering devices disposed along the casing. When the pressure reaches a predetermined maximum, the disc 57 will be sheared out of the plug passage 56, to automatically relieve the pressure and thereby prevent the springs from being subjected to too great an expanding force.

It is, accordingly, apparent that a casing centering device has been provided, in which the springs are disposed in a comparatively retracted position during the lowering of the casingthrough the well bore, as well as through the surface casing near the top of the well bore, the springs being in an `inward position to offer comparatively little resistance, if any, to the lowering movement of the casing. However, the outward bowed height of the springs, as well as the force of the springs against the formation, can be increased by the movement of the upper cylinder or collar 24` toward the lower collar 20, to insure a positive centering force urging and maintaining the casing string in a substantially centered position within the well bore. The centering force is prevented from exceeding a predetermined value to insure against the destruction of any of the springs, the centering devices all remaining intact and capable of performing their required centering function.

The inventor claims:

l. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed in circumferentially spaced relation around the exterior of said body; rst means conning the lower portions of said springs adjacent said body; second means conlining the upper portions of said springs adjacent said body; one of said means including a surface responsive to the pressure of fluid internally of said tubular body for shifting said first and second means longitudinally with respect to each other to shift the intermediate portions of said springs laterally of said body; means providing fluid communication between said surface and the interior of said tubular body; and means in the conduit string for relieving the fluid pressure in the conduit string and said tubular body when the fluid pressure reaches a predetermined maximum value.

2. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed in circuferentially spaced relation around the exterior of said body; first means confining the lower'portions of said springs adjacent said body; second means contining the upper portions of said springs adjacent said body; one of said means including a surface responsive to the pressure of fluid internally of said tubular body for shifting said tirst and second means relatively toward each other to bow the intermediate portions of said springs laterally outward; means providing duid communication between said surface and the interior of said tubular body; means for preventing said iirst and second means from moving relatively away from each other; and means in the conduit string for relieving the fluid pressure in the conduit string and said tubular body when the fluid pressure reaches a predetermined maximum value.

3. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed in circumferentially spaced relation around the exterior of said body; a lower collar engaging the lower portions of said springs to secure said lower portions adjacent said body; an upper collar engaging the upper portions of said springs to conne said upper portions adjacent said body; said body having a side port; one of said collars comprising a hydraulic cylinder slidably and sealingly engaging saidl body on opposite sides of said port, whereby Huid under pressure can be fed through said port into said cylinder to shift said cylinder along said body toward the other of said collars to bow the intermediate portions of said springs laterally outward.

4. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed in circumferentially spaced relation around the exterior of said body; a lower collar engaging the lower portions: of said springs to secure said lower portions adjacent said body; an upper collar engaging the upper portions of said springs to confine said upper portions adjacent said body; said body having a side port; one of said collars comprising a hydraulic cylinder slidably and sealingly engaging said body on opposite sides of said port, whereby fluid under pressure can be fed through said port into said cylinder to shift said cylinder` along said body toward the other of said collars to bow the intermediate portions of said springs laterally outward; and one-way lock means engageable with said one collar and body to permit said cylinder to move on said body toward the other collar but to prevent reverse movement of said cylinder on said body.

5. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed in circumferentially spaced relation around the exterior of said body; a lower collar engaging the lower portions of said springs to secure said lower portions adjacent said body; an upper collar engaging the upper portions of said springs to confine said upper portions adjacent said body; said body having a side port; one of said collars and said body being so arranged with respect to each other that fluid under pressure from said port is directed onto said one collar to shift said one collar along said body toward the other of said collars to bow the intermediate portions of said springs laterally outward; and means in the conduit string for relieving the fluid pressure in the conduit string and said tubular body when the fluid pressure reaches a predetermined maximum value.

6. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed. in circurnferentially spaced relation around the exterior of said body; a lower collar engaging the lower portions of said springs to secure said lower portions adjacent said body; an upper collar engaging the upper portions of said springs to confine said upper portions adjacent said body; said body having a side port; one of said collars and said body being so arranged with respect to each other that fluid under pressure from said port is dire-cted onto said one collar to shift said one collar along said body toward the other of said collars to bow the intermediate portions of said springs laterally outward; one-way lock means engageable with said one collar and body to permit said one collar to move on said body toward the other collar but to prevent reverse movement of said one 7 collar on said body; and means in the conduit string for relieving the iiuid pressure in the conduit string and said tubular body when the iiuid pressure reaches a predetermined maximum value.

7. In apparatus for centering conduit strings in well bores as defined in claim 6; wherein said last-mentioned means comprises a disruptable disc extending across the conduit string to restrict downward passage of fluid in the conduit string and tubular body, said disc being disrupted when the fluid pressure in the conduit string reaches a predetermined maximum value.

8. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf. springs disposed in circumferentially spaced relation around the exterior of said body; a lower collar engaging the lower portions of said springs to secure said lower portionsadjacent said body; an upper collar engaging the upper portions of said springs to confine said upper portions adjacent said body; said body having a side port; one of said collars comprising a hydraulic cylinder slidably and sealingly engaging said body on opposite sides of said port, whereby tluid under pressure can be fed through said port into said cylinder to shift said cylinder along said body toward the other of said collars to bow the intermediate portions of said springs laterally outward; and means in the conduit string for relieving the fluid pressure in the conduit string and said tubular body when the iiuid pressure reaches a predetermined maximum value.

9. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality of leaf springs disposed in circumferentially spaced relation around the exterior of said body; a lower collar engaging the lower portions of said springs to secure said lower portions adjacent said body; an upper collar engaging the upper portions of said springs to confine said upper portions adjacent said body; said body having a side port; one of said collars comprising a hydraulic cylinder slidably and sealingly engaging said body on opposite sides of said port, whereby fluid under pressure can be fed through said port into said cylinder to shift said cylinder along said body toward the other of said collars to bow the intermediate portions ofsaid springs laterally outward; means in the conduit string for relieving the fluid pressure in the conduit string and said tubular body when the liuid pressure reaches a predetermined maximum value; and one-way lock means engageable with said one collar and body to permit said cylinder to move on said body toward the other collar but to prevent reverse movement of said cylinder on said body. Y

10. In apparatus for centering conduit strings in well bores: a tubular body adapted to form part of a conduit string; a plurality ofleaf springs disposed in circumferentially spaced relation around the exterior of said body; rst means confining the lower portions of said springs adjacent said body; second means confining the upper portions of said springs adjacent said body; at least one of said means including a surface responsive to internal fluid pressure of said tubular b ody; said tubular body having a port establishing tluid communication between the interior of said tubular body and said surface whereby said surface is responsive to the pressure of iiuid internally of said tubular body to shift said first and second means longitudinally with respect to each other to shift the intermediate portions of said springs laterally of said body; and means in the conduit string for relieving the fluid of pressure in the conduit string and said tubular body when the uid pressure reaches a predetermined maximum value.

References Cited in the le of this patent UNITED STATES PATENTS 1,286,141 Stumpf Nov. 26, 1918 1,801,353 Lane et al. Apr. 21, 1931 2,170,527 Culbertson Aug. 22, 1939 2,311,768 McCray Feb. 23, 1943 2,712,920 Cullen et al. July 12, 1955 

